Impaired receptor binding and decrease in isoelectric point of lactoferrin after interaction with human monocytes.

Abstract

The iron-binding glycoprotein lactoferrin binds to specific receptors on human monocytes as an initial step implicated in monocytic iron deposition. In this study, the properties of lactoferrin were studied after its interaction with human monocytes. Rebinding of lactoferrin to its monocytic receptor was grossly impaired and a small decrease in isoelectric point from 8.9 to 8.8 was observed. In contrast, antigenic and iron-binding properties of lactoferrin were preserved, the molecular weight by SDS-polyacrylamide gel electrophoresis was unchanged and no low-molecular fragments were detected by gel-filtration. These findings indicate that lactoferrin molecules cannot operate in a cyclic manner to deposit iron. Furthermore, these results might contribute towards explaining the complex disappearance kinetics observed for lactoferrin in plasma.